Multiple impregnation of papermaker&#39;s felt



i atentec l Sept. 4, 1951 MULTIPLE :IMPREGNATION OF PAPER- i n fWilliamv.13 eIjgZIiInd, Dayton,-hio, v assignor to The On "Felt ftBlanlietflnnapariy, 159351113, Ohio, a-corporationpf Ohio This invention-relates,t fe t for 'nape ims ing or like machines. andtoa method-pfpreparing suchfelts. I

.It .isan object of this invention to provide paper making or like feltswhich" have'ahigh 'degree of wettability and a low wetting time.

It is another object ofthis invention'to provide paper making or likefelts which have a high degree of abrasion resistance.

"These and other objects are accomplishedby first impregnating-the feltwith an aqueous solution of synthetic resin, curing and ageing saidresin,'therea'fter' impregnating the pretreated'felt with an aqueousemulsion of synthetic rubber and curing said rubber material.

As the resin, urea-formaldehyde resins and phenol'-formaldehyde resinswere found most suitable; however, any other water soluble-syntheticresin is operative. A solution having a concentration of from 10 to 30%is the range preferred. The same concentration was usedin thelatex-containing emulsion 4 for the second treatment.

The latices giving particularly -;-good results were butadieneacrylonitr-ile copolymers, butadiene styrene copolymers, and-neoprene.However, other synthetic-rubbers are also operative.

The felts usually contain -moreor "Jess -ac-id which-originates frompretreating processes neutralization of this acid is necessary in orderto obtain uniform impregnation-"of:irubbers 'lto .the felts. If thisacidis not neutralized thelimpregnating solution will change :fromitsialkalil state to an acid state and the" rubberorulatexwillprecipitate on-kick-out :and be of -11o value asanimpregnant. For this reason, the impregnating emulsons are preferablygiven aEpH of tat-leash? This may bedone. by any alkaline ..solution..zI have used ammonia L solution with .ad-vantageifor this purpose. Theamount of alkalidependent upon the vpH of the rubber emulsion andonvtheacid-contentof the felt.

"The felts may 'be impregnated by any method known-in the: art showever,I prefer :to apply. the liquids by-immersion. The timeof immersionr-isadjusted according to the pick-up desired. *A total pick-up of from 1 to25% by weight of cured resinous and --rubber -ingredients-w-ith--reg-ard-to thedried felt materials was*found-;satis-factory, from 12to 25% representing the preferred range.

If, desired, curing catalysts, such as diamrpoum ph pha e, tarta i acidotassi te raoxalate or the like maybe added tothe esin solut on .iL kewiW t n en s ay: be a'dmixed thereto. j'I witchell oilgfor exampleywa'sfound most satisfactory v for this purpose.

. 7 )2 In the sfollowing .a few iexamples ..a ;e.;giv.en whichillustrate the pllocess of my invention.

Example I Mixtss q ltflr a ldkifi esiia 100 grams 60% solution of ureaformaldehyde resin.

500 grams water.

12 grams ammonium :hyd 9xide428%).

The felt was dipped in a mixture of 'the above composition and theexcess then removed .;,by squses a iih ielilik sa h s. h n. ui a app ximfil 2W j ..9 $129 4 .1 .3 9 .a allowed to age over night. The pick-upwas 11%. Thereafter the felt,:was impregnated with a rubber emulsion.

ixtu iorss ond izsii rg eeti 10.0 ram l istedieee lashs i r eealr eer(aqueous emulsion w ith i solids content). 300 grams water. 4 gramsammonia (28%;)

-.;inl.os ls .t

The felt was agaimfidu.

es ismulsi n $1931 9. ,Q1I ,5 F- ,2 hours. The second pick-up amguntedto 1,0 The felt treated with the materials and-by themethod-set:fortninnthisi exampleashowedlan .increaselof the wetcabrasienaesistanee gf approximately 133% as compared with that of ethenntreated wet felt. .The time reguiredjor completely wetting the felts'thus impregnated was m n tesandiaf'kzsa miqswil 1. .19 5- up then was162% and the water retention after squeezing of the felts was 72%. Thisamounts to awater differential ofwh-ich ill-ustrates .-.the actualwaterabsorption-cap acity sof trie -felts .in operation.

vEscample II Mixture for first impregnation;

100. grams..-..6fi% solution ofsui'ea tformalds ix resin.

500.=grams water.

1- gramrTwi-tchell oil.

L2 grams-.ammonia i2 8;%)..

Example III First dip:

100 grams urea formaldehyde resin solution 500 grams water.

1 gram Twitchell oil.

1 gram diammonium phosphate. 1 gram tartaric acid.

For the second dip the same rubber emulsion was used as in Example I.Curing and ageing were substantially carried out as described in ExampleI. The pick-ups were 8% for the first and 6% for the secondimpregnation. In this instance, the wet abrasion resistance wasincreased by 107%. The wetting time was 52 minutes and 18 seconds.

The total water pick-up amounted to 137%, the- Second clip:

The composition of the latex used in this example was identical withthat of Example I,

The pick-ups were 8% and 13%, respectively. The increase of the abrasionresistance amounted to 117% and the wetting time to 29 minutes and 18seconds. The water pick-up was 154%, the water retention after squeezing77% and the water differential also 77%.

Example, V

Mixture for first impregnation:

100 grams phenol formaldehyde resin (50%). 400 grams Water.

The impregnated felt wascured at substantially 230 F. for 1 hourandthereafter for another hour at 285 F.

Mixture for second impregnation:

Latex and conditions were the same as in Example I.

The pick-ups were .7 and 11%, respectively. The wet abrasion resistanceof the treated felt was increased by 123% and the wetting time was 70minutes and 30 seconds. The water pick up amount- 4 Second impregnationstep 100 grams 47 emulsion of neoprene. 370 grams water.

wet and dry, were also essentially increased.

These increases were 21% and 26% for the dry and wet warp threads,respectively, and 22% and 17% for the dry and wet filler threads,respeced to 159%, the water retention to 76% and the water differentialto 83%.

In this example the tensile strength was also increased by thetreatment. Thus, thetensile strength of the warp threads increased by16% in the dry condition and by 15% in wet condition, whereas thetensile strength of the filler threads increased by 30% in dry and by 8%in the wet condition.

Example VI First impregnation step:

The resin was cured as in Example 5. The pickup amounted to 15%.

tively.

It will thus be seen from Examples V and VI that the phenol formaldehyderesins havethe outstanding property of increasing the tensile strengthsof both warp and filler threads, a feature which might become a decisivefactor with regard to a great many uses of such impregnated felts.

It will be understood that while there have been described hereincertain specific embodiments of the invention, it is not intendedthereby to have it limited to or circumscribed by the details given,since the invention is susceptible to various modifications and changeswhich come within the spirit of the disclosure and the scope of theappended claims.

I claim:

1. A method of treating felts for paper making machines which comprisesloading a dimensionally stable woven wool base with an aqueous solutionof resin selected from the group consisting of urea-formaldehyde andphenol-formaldehyde resins, removing excess resin, curing said resin,loading the resin coated wool base with an aqueous emulsion of asynthetic rubber, removing the excess emulsion whereby the total pickupor coating solids is limited to between about 10 and 25%, said rubberbeing selected from the group consisting of acrylonitrile-butadienecopolymer, styrene-butadiene copolymer, and polychloroprene, and curingsaid deposited synthetic rubber impregnation.

2. The method of treating felts for paper making machines whichcomprises loading a dimensionally stable Woven wool base with an aqueoussolution of resin selected from the group consisting ofurea-formaldehyde and phenol-formaldehyde resins, removing excess resinwhereby the pickup of resin is limited tobetween approximately 5 and15%, curing said resin, loading the resin coated Wool base with anaqueous solution of a synthetic rubber, said rubber being selected fromthe group consisting of acrylonitrilebutadiene copolymer,styrene-butadiene copolymer, and polychloroprene, removing the excessemulsion whereby the total pickup of coating solids is limited tobetween approximately 10 and 25%, and curing said deposited syntheticrubber.

3. The method of treating felts for paper making machines whichcomprises loading a dimensionally stable woven wool base with an aqueoussolution of resin selected from the group consisting ofurea-formaldehyde and phenolformaldehyde resins, removing excess resinwhereby the pickup of resin is limited to between approximately 5' and15%, curing said resin at approximately 200 to 300 F. for about twohours, loading the resin coated wool base with an aqueous solution of asynthetic rubber, said rubber being selected from the group consistingof acrylonitrile-butadiene copolymer, stydene-butadiene copolymer, andpolychloroprene, removing the excess emulsion whereby the total pickupof coating solids is limited to between approximately 10 and 25%, andcuring said deposited synthetic rubber at about 250 F. for approximatelytwo hours.

4. As a new article of manufacture, a felt for paper making machinescomprising a dimen sionally stable woven wool base impregnated with 5 to15% by weight of a resin selected from the group consisting ofurea-formaldehyde and phenol-formaldehyde resins, a superimposed layerof synthetic rubber, said rubber being selected from the groupconsisting of acrylonitrile-butadiene copolymer, styrene-butadienecopolymer, and polychloroprene, and the total pick-up of coating beinglimited to between approximately 10 and 25% whereby the fibers remainunmatted.

5. As a new article of manufacture, a felt for paper making machinescomprising a dimensionally stable woven wool base impregnated with aREFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,967,863 Collins et al July 24,1934 2,038,712 Brodin Apr. 28, 1936 2,211,951 Hershberger Aug. 20, 19402,211,959 Maney Aug. 20, 1940 2,327,573

OTHER REFERENCES PaperTrade J. of November 5, 1942, pages 239-242.

Walsh Aug. 24, 1943

1. A METHOD OF TREATING FELTS FOR PAPER MAKING MACHINES WHICH COMPRISESLOADING A DIMENSIONALLY STABLE WOVEN WOOL BASE WITH AN AQUEOUS SOLUTIONOF RESIN SELECTED FROM THE GROUP CONSISTING OF UREA-FORMALDEHYDE ANDPHENOL-FORMALDEHYDE RESIN, REMOVING EXCESS RESIN, CURING SAID RESIN,LOADING THE RESIN COATED WOOL BASE WITH AN AQUEOUS EMULSION OF ASYNTHETIC RUBBER, REMOVING THE EXCESS EMULSION WHEREBY THE TOTAL PICKUPOF COATING SOLIDS IS LIMITED TO BETWEEN ABOUT 10 AND 25%, SAID RUBBERBEING SELECTED FROM THE GROUP CONSISTING OF ACRYLONITRILE-BUTADIENECOPOLYMER, STYRENE-BUTADIENE COPOLYMER, AND POLYCHLOROPRENE, AND CURINGSAID DEPOSITED SYNTHETIC RUBBER IMPREGNATION.